Gram-negative disease and its most serious complications, e.g., bacteremia and endotoxemia, are the cause of significant morbidity and mortality in human patients. This is particularly true of the gram-negative organism Pseudomonas aeruginosa, which has been increasingly associated with bacterial infections, especially nosocomial infections, over the last fifty years.
During the past few decades, antibiotics have been the therapy of choice for control of gram-negative disease. The continued high morbidity and high mortality associated with gram-negative bacterial disease, however, is indicative of the limitations of antibiotic therapy particularly with respect to P. aeruginosa. (See, for example, Andriole, V. G., "Pseudomonas Bacteremia: Can Antibiotic Therapy Improve Survival?" J. Lab. Clin. Med. (1978) 94: 196-199). This has prompted the search for alternative methods of prevention and treatment.
One method that has been considered is augmentation of the host's immune system by active or passive immunization. For instance, it has been observed that active immunization of humans or experimental animals with whole cell bacterial vaccines or purified bacterial endotoxins from P. aeruginosa leads to the development of specific opsonic antibodies directed primarily against determinants on the repeating oligosaccbaride units of the lipopolysaccharide (LPS) molecules located on the outer cell membrane of P. aeruginosa (see Pollack, M., Immunoglobulins: Characteristics and Uses of Intravenous Preparations, Alving, B. M. and Finlayson, J. S., eds, pp. 73-79, U.S. Department of Health and Human Services, 1979). Such antibodies, whether actively engendered or passively transferred, have been shown to be protective against the lethal effects of P. aeruginosa infection in a variety of animal models (Pollack, supra) and in some preliminary investigations with humans (see Young, L. S. and Pollack, M., Pseudomonas aeruginosa, Sabath, L., ed., pp. 119-132, Hans Huber, 1980). Moreover, of particular importance to the role of these antibodies in humans has been the finding in patients with P. aeruginosa bacteremia of an association between survival and high acute serum titers of antibodies to the LPS molecules of the infecting strain (see Pollack, M., and Young, L. S., J. Clin Invest., 63: 276-286, (1979)).
The above reports suggest that immunotherapeutic approaches could be utilized to prevent and treat bacterial disease due to P. aeruginosa, such as by administering pooled human immune globulins that contain antibodies against the infecting strain(s). Human immune globulins are defined herein as that portion of fractionated human plasma that is enriched for antibodies, among which are represented specific anti-bodies to strains of P. aerginosa. Due to certain inherent limitations in using human immune globulin components, this approach to treatment of disease due to P. aeruginosa remains under investigation (see, for example, Collins, M. S. and Roby, R. E., Am. J. Med., 76(3A):168-174, (1984)), and as yet there are no commercial products available utilizing these components.
One such limitation associated with immune globulin compositions is that they consist of pools of samples from a thousand or more donors, such samples having been preselected for the presence of particular anti-Pseudomonas antibodies. This pooling leads to an averaging of individual antibody titers which, at best, results in modest increases in the resultant titer of the desired antibodies.
Another limitation is that the preselection process itself requires expensive, continuous screening of the donor pool to assure product consistency. Despite these efforts, the immune globulin products can still have considerable variability from batch to batch and among products from different geographic regions.
Yet another such limitation inherent in immune globulin compositions is that their use results in the coincident administration of large quantities of extraneous proteinaceous substances (which may include viruses, such as those recently shown to be associated with Acquired Immune Deficiency Syndrome, or AIDS), having the potential to cause adverse biologic effects. The combination of low titers of desired antibodies and high content of extraneous substances may often limit, to suboptimal levels, the amount of specific and thus beneficial immune globulin(s) administrable to the patient.
There exists in the literature a number of serotyping schema that are useful for analyzing Pseudomonas aeruginosa infections. The schema are primarily based on the heat-stable major somatic antigens of this organism (see Zierdt, C. H., in Glucose Nonfermenting Gram-Negative Bacteria in Clinical Microbiology, Gilardi, G. L., ed., CRC Press, pp. 213-238 (1978)). The proliferation of the serogrouping schema has made serological studies of P. aeruginosa. rather difficult to compare, and thus the choice of any given system for the purpose of screening supernatants would seem somewhat arbitrary. The confusion between typing systems was recently clarified by the creation of the International Antigenic Typing Scheme (IATS) system which was proposed by the Subcommittee on Pseudomonadaceae of the International Committee on Systematic Bacteriology as the backbone for further serological study of P. aeruginosa. This system, which provides for seventeen distinct serotypes, designated IATS Type 1, IATS Type 2, etc., encompasses all the heat-stable major somatic antigens identified in previous systems. See Liu, P. V., Int. J. Syst. Bacteriol., 33: 256-264, (1983), which is incorporated herein by reference.
In developing protective monoclonal antibodies that are cross-reactive among strains of P. aeruginosa, it is also advantageous to incorporate a typing scheme which is based on the protective antigens of P. aeruginosa. Such a scheme has been devised with the intention of developing a vaccine for clinical use and is described in detail in Fisher, M. W. et al., J. Bacteriol., 98: 835-836, (1969). This system, commonly referred to as the Fisher typing system, classifies the majority of known P. aeruginosa into seven types, designated Fisher immunotype 1, Fisher immunotype 2, etc. Correlation between the IATS and Fisher typing systems has been clarified (see Liu, P. V., et al., supra) and is presented in Table I. As noted in Table I, there are no corresponding Fisher immunotypes for certain IATS serotypes, although each Fisher immunotype does correspond to a certain IATS serotype. For the IATS and Fisher typing systems, the antigenic determinants relevant to both serotyping schemes are believed to reside on the surface LPS molecules of P. aeruginosa (Liu, P. V. et al., supra; Hanessien, F., et al., Nature, 229: 209-210 (1979)).
TABLE I ______________________________________ Comparison and Correlation of the IATS and Fisher Typing Schemes for Pseudomonas aeruginosa IATS Fisher ______________________________________ 1 4 2 3 3 -- 4 -- 5 7 6 1 7 -- 8 6 9 -- 10 5 11 2 12 -- 13 -- 14 -- 15 -- 16 -- 17 -- ______________________________________
In 1975 Kohler and Milstein reported their seminal discovery that certain mouse cell lines could be fused with mouse spleen cells to create hybridomas each of which which would secrete antibodies of a single specificity, i.e., monoclonal antibodies (Kohler, G., and Milstein, C., Nature, 256: 495-497 (1975)). With the advent of this technology it became possible, in some cases, to produce large quantities of exquisitely specific murine antibodies to a particular determinant or determinants on antigens. Such mouse monoclonal antibodies or compositions of such antibodies may, however, have major disadvantages for use in humans, particularly in light of the finding that mouse monoclonal antibodies when used in trial studies for the treatment of certain human disease have often been observed to elicit an immune response that renders them noneffective (Levy, R. L. and Miller, R. A., Ann. Rev. Med., 34: 107-116, (1983)).
Using hybridoma technology, Sadoff et al. have reported the production of a mouse monoclonal antibody of the IgM class directed against an O-side chain determinant on the LPS molecules of a particular serotype of P. aeruginosa (Abstracts of the 1982 Interscience Conference on Antimicrobial Agents and Chemotherapy, No. 253). They further reported that this murine antibody protected mice against a lethal challenge of P. aeruginosa of the same serotype as the type to which the antibodies were directed (i.e., the homologous serotype). Several subsequent articles have detailed the development of mouse and human anti-P. aeruginosa LPS monoclonal antibodies of various specificities; for example: Sawada, S., et al., J. Inf. Dis., 150: 570-576, (1984); Sadoff, J., et al., Antibiot. Chemother., 36: 134-146, (1985); Hancock, R., et al., Infect. Immun. 37: 166-171 (1982); Siadak, A. W. and Lostrom, M. E., in Human Hybridomas and Monoclonal Antibodies, Engleman, E. G., et al. eds., pp. 167-185, Plenum Publishing Corp. (1985) and Sawada, S. et al., J. Inf. Dis., 152: 965-970, (1985). Production and immunotherapeutic application of anti-P. aeruginosa LPS sero-type-specific human monoclonal antibodies are disclosed in pending U.S. patent application Nos. 734,624 and 828,005, which are incorporated herein by reference.
While certain advantages may exist for utilizing monoclonal antibodies specific for a single IATS serotype of P. aeruginosa in some situations, such as when infection can be traced to a single serotype, in many other situations they would not be preferred. For example, in prophylactic treatments for potential infections in humans, it would be preferable to administer a human antibody or antibodies protective against a plurality of IATS serotypes. Similarly, in therapeutic applications where the serotype(s) of the infecting strain(s) is not known, it would be preferable to administer a human antibody or antibodies effective against most, If not all, of the clinically important P. aeruginosa IATS serotypes. Whereas a combination of human monoclonal antibodies, each specific for a single IATS serotype of P. aeruginosa, theoretically might be formulated to protect against the various serotypes, such a composition would be difficult to develop and, from a manufacturing standpoint, uneconomical to produce.
Accordingly there exists a significant need for human anti-P. aeruginosa monoclonal antibodies capable of recognizing and providing protection against multiple IATS serotypes of P. aeruginosa. Further, these antibodies should be suitable for use as prophylactic and therapeutic treatments of P. aeruginosa infections. The present invention fulfills these needs.